TACHINID PARASITES OF THE GIPSY MOTH. 



219 



In its method of attack Compsilura is the opposite of Blepharipa. 

 Its eggs hatch in the uterus of the mother, and the tiny magots are 

 deposited beneath the skin of the host caterpillar by means of a 

 sharp, curved "larvipositor," which is situated beneath the abdomen. 

 They usually seek the alimentary canal, in the walls of which they 

 establish themselves during the first stage of their larval existence. 



Growth is rapid, and in the summer is in no way correlated with 

 the growth and development of the host. About two weeks are 

 required for the complete development of the maggot, irrespective 

 of the stage of the host at the time of attack, and at the end of that 

 period it issues, and usually drops to the ground for pupation. The 

 puparia from maggots which issue from caterpillars which have spun 

 for pupation are not infrequently found in the cocoons in the case of 

 the brown-tail moth; 

 and even in the case 

 of the gipsy moth, 

 which does not spin 

 cocoons worthy of the 

 name, the puparia are 

 often found immedi- 

 ately associated with 

 the host remains. 



It requires a sur- 

 prisingly short time 

 for the females to at- 

 tain full sexual matur- 

 ity after their emer- 

 gence, three or four 

 days apparently being 

 sufficient. This, with 

 two weeks for the 

 growth of the larva, and one week, or perhaps a little more, for the 

 pupal period, makes possible a generation every four weeks during 

 the warmer months of the year. 



The position of the larva in the alimentary canal, together with 

 certain structural characteristics, consisting of minute anal hooks, 

 which are only known amongst other first-stage tachinids in the very 

 similar genus Dexodes, makes possible the quite accurate determina- 

 tion of Compsilura concinnata from its first-stage larva alone, and 

 only from observations which have been made upon these larvse is 

 it possible to say anything definite and at first hand concerning its 

 habits of hibernation. Larvae, which are almost certainly Compsi- 

 lura concinnata, have been occasionally found in living brown-tail 

 moth caterpillars during the winter months. It is presumed if these 

 larvse were able to mature under these circumstances, that they 



Fig. 41. 



-Compsilura concinnata: Adult female and details, 

 enlarged. (Original.) 



Much 



